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Herrerasaurus
Herrerasaurus was an early dinosaur from the Triassic of Argentina. Description Herrerasaurus is estimated to have measured 3 meters or more in length and up to 350 kilograms in weight.Paul, G.S. (1988). Predatory Dinosaurs of the World. New York: Simon and Schuster. pp. 248–250. ISBN 0-671-68733-6. It had a fairly typical theropod body plan, but its skull more resembled those of earlier and more primitive archosaurs.Sereno, P.C.; and Novas, F.E. (1993). "The skull and neck of the basal theropod Herrerasaurus ischigualastensis". Journal of Vertebrate Paleontology 13 (4): 451–476. doi:10.1080/02724634.1994.10011525. Classification Herrerasaurus and its closest relatives form the family Herrerasauridae. However, where the herrerasaurs fit in the early evolutionary tree of dinosaurs is unclear. Most studies have found them to be basal theropods, although it is possible that they are basal saurischians or even non-dinosaurian archosaurs.Brinkman, D.B.; and Sues, H.-D. (1987). "A staurikosaurid dinosaur from the Upper Triassic Ischigualasto Formation of Argentina and the relationships of the Staurikosauridae". Palaeontology 30: 493–503.Ezcurra, M.D. (2010). "A new early dinosaur (Saurischia: Sauropodomorpha) from the Late Triassic of Argentina: a reassessment of dinosaur origin and phylogeny". Journal of Systematic Palaeontology 8 (3): 371–425. doi:10.1080/14772019.2010.484650. Discovery Incomplete remains of Herrerasaurus were discovered in the Ischigualasto Formation of Argentina, and named in 1963 by paleontologist Osvaldo Reig after the rancher who first noticed the fossils.Reig, O.A. (1963). "La presencia de dinosaurios saurisquios en los "Estratos de Ischigualasto" (Mesotriásico Superior) de las provincias de San Juan y La Rioja (República Argentina)". Ameghiniana (in Spanish) 3 (1): 3–20. It was first believed that the remains were from an early type of carnosaur, but over the following years Herrerasaurus was classified on separate occasions as a theropod, a prosauropod, an indeterminate saurischian, and non-dinosaurian.Gauthier, J.A., Cannatella, D., Queiroz, K., Kluge, A.G., and Rowe, T. (1989). "Tetrapod phylogeny". In Fernholm, K. Bremer, & Jörnvall, H. The Hierarchy of Life. Amsterdam: Elsevier Science Publishers B. V. pp. 337–353. The next significant discovery of Herrerasaurus fossils was in 1988, when a complete skull was discovered by Paul Sereno and colleagues.Sereno, P.C.; and Novas, F.E. (1992). "The complete skull and skeleton of an early dinosaur". Science 258 (5085): 1137–1140. Bibcode:1992Sci...258.1137S. doi:10.1126/science.258.5085.1137. PMID 17789086. Paleoecology Environment It is believed that the Ischigualasto Formation was a volcanically active floodplain during the Middle and Late Triassic period when Herrerasaurus lived. The climate was typically warm and moist, although the area experienced seasons throughout the year.Columbi, Carina E. (2008-10-05). "Stable isotope analysis of fossil plants from the Upper Triassic Ischigualasto Formation in the northwest of Argentina". Houston, TX: The Geological Society of America. Retrieved 2009-07-23. Ferns and conifers were likely the dominant vegetation, forming high-altitude forests.Bonaparte, J.F. (1979). "Faunas y paleobiogeografía de los tetrápodos mesozoicos de América del Sur". Ameghiniana, Revista de la Asociación Paleontológica Argentina (in Spanish) 16 (3–4): 217–238. It coexisted with the early dinosaur Eoraptor, which was also found in the Ischigualasto Formation. Paleobiology Diet Herrerasaurus was a carnivore, and likely preyed on smaller animals. Coprolites found in the Ischigualasto Formation have been assigned as belonging to Herrerasaurus, and if this identification is correct it is evidence that the dinosaur could digest bone.Hollocher, K.T.; Alcober, O.A.; Colombi, C.E.; and Hollocher, T.C. (2005). "Carnivore coprolites from the Upper Triassic Ischigualasto Formation, Argentina: chemistry, mineralogy, and evidence for rapid initial mineralization". PALAIOS 20: 51–63. doi:10.2110/palo.2003.p03-98. Pathologies One specimen of Herrerasaurus exhibits unusual pitting in the skull bones. This has been attributed to an infected head injury that later healed. It is likely that these injuries were obtained during a fight with another Herrerasaurus.Molnar, R. E., 2001, Theropod paleopathology: a literature survey: In: Mesozoic Vertebrate Life, edited by Tanke, D. H., and Carpenter, K., Indiana University Press, p. 337-363. References Category:Animals Category:Carnivores Category:Dinosaurs Category:Theropods Category:Fossil taxa described in 1963